Wheelchair lifts mounted on vehicles, such as buses, vans, motor homes and automobiles, provide wheelchair users access to the interior of the vehicles thereby increasing their mobility and enabling these people to become more self-reliant and independent. Wheelchair lifts have generally horizontal platforms which are used to support manual and motor driven wheelchairs along with persons located on the wheelchairs. Lift structures connected to the platforms operate to selectively raise and lower the platforms. When the platforms are in the lower or ground positions the wheelchairs are moved onto the platforms. The platforms are raised by the lift structures to a selected elevation, such as the floor of the vehicle, and then moved off the platform into the interior compartment of the vehicle. Actuators, such as electric motors, operating screws and hydraulic cylinders, are used to move the platforms to transport positions within the confines of the vehicle. The wheelchair is secured to the vehicle floor prevent inadvertent movement of the wheelchair within the vehicle. In some vehicles, the wheelchair is moved to a vehicle operator position and anchored thereto to allow the wheelchair user to operate the vehicle. Examples of wheelchair lifts are disclosed in the following U.S. patents.
R. W. Braun et al in U.S. Pat. No. 4,664,584 describes a rotary wheelchair lift having a platform vertically moveable with a hydraulic lift. A linear actuator operates to rotate the platform and the hydraulic lift to a position inside the passenger compartment of the vehicle.
C. L. Wolfe in U.S. Pat. No. 5,052,879 discloses a wheelchair lift operable by a person in a wheelchair to elevate and move the wheelchair from a ground position to a motor vehicle driver position without leaving the wheelchair. The lift has a frame and horizontal platform for supporting a wheelchair adjacent the drivers side of a motor vehicle. Seven actuators including a first pair of piston and cylinder units secured to the frame operate to raise the frame and platform to the level of the floor of the vehicle and move the platform to the vehicle driving position. The platform supporting the wheelchair is laterally moved from the frame onto a pair of tracks secured to the floor of the vehicle. The pair of piston and cylinder units used to lift the platform limits foot clearance during lateral movement of the platform. A motor driven endless chain on the platform operates to transfer the platform to and from the tracks. When the platform is mounted on the tracks, the wheelchair is the vehicle driving position. The tracks are U-shaped members secured directly to the vehicle's floor. The platform supporting the wheelchair is located above the tracks. Snow, water, mud and dirt can accumulate and freeze in the tracks causing the lift to jam. The tracks and platform are not vertically adjustable to accommodate short and tall persons. A ramp pivotally connected to the platform facilitates the movement of the wheelchair onto and off of the platform. The ramp and platform fold to upright positions which limits the space on the platform for the wheelchair and provides a rear support behind the wheelchair. All of the piston and cylinder units and motor for the endless chain are controlled with a control box mounted on one side of the platform.
J. E. Crain et al in U.S. Pat. No. 5,308,214 discloses a wheelchair lift apparatus having a wheelchair support platform moveable to a position adjacent the outside of the driver's seat of a motor vehicle to allow a person to move out of the wheelchair into the driver's seat. The platform is vertically moveable to lift the wheelchair from a ground position to an up position and then swing the platform behind the driver's seat. A horizontal motor driven screw laterally moves the platform into the rear passenger compartment of the vehicle.
R. X. Meyer in U.S. Pat. No. 5,466,111 discloses an apparatus and method for loading a wheelchair into a vehicle driving position. The wheelchair is attached to the open door of the vehicle. The wheelchair vertical lift is used to lift the wheelchair off the ground to allow the door to close and position the wheelchair in the vehicle driving position. A locking mechanism is used to secure the wheelchair in the driving position.
D. L. Jones et al discloses in U.S. Pat. No. 5,746,465 an apparatus operable to move a person on a seat through a vehicle driven side door to a driving position of a motor vehicle. The seat is pivotally mounted on a portion of the vehicle's frame. The seat is vertically and horizontally moveable with motor driven screws to position the person in a convenient location behind the vehicle's steering wheel.
D. L. Mortimore in U.S. Patent Application Publication 2001/0026756 discloses a lift operable to elevate and laterally move a person transport vehicle from a ground position to the floor level of a motor vehicle, such as a van. The lift has tracks secured to the floor of the van supporting a plate. A first actuator connected to the plate causes the plate to reciprocate along the tracks. A lift assembly having parallel linkages is secured to the plate. A second actuator operates the lift assembly to raise and lower a platform for supporting a person transport vehicle. When the platform is in the raised position, the first actuator is operated to laterally move the folded parallel linkages and platform supporting the person transport vehicle into the van.